<meta charset="utf-8">
(#) Calls to `launch` should happen inside of a SideEffect and not during composition

!!! ERROR: Calls to `launch` should happen inside of a SideEffect and not during composition
   This is an error.

Id
:   `LaunchDuringComposition`
Summary
:   Calls to `launch` should happen inside of a SideEffect and not during composition
Severity
:   Error
Category
:   Correctness
Platform
:   Any
Vendor
:   Jetpack Activity Compose
Identifier
:   androidx.activity.compose
Feedback
:   https://issuetracker.google.com/issues/new?component=612128
Min
:   Lint 8.0 and 8.1
Compiled
:   Lint 8.0 and 8.1
Artifact
:   [androidx.activity:activity-compose](androidx_activity_activity-compose.md.html)
Since
:   1.4.0
Affects
:   Kotlin and Java files and test sources
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/activity/activity-compose-lint/src/main/java/androidx/activity/compose/lint/ActivityResultLaunchDetector.kt)
Tests
:   [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/activity/activity-compose-lint/src/test/java/androidx/activity/compose/lint/ActivityResultLaunchDetectorTest.kt)
Copyright Year
:   2021

Calling `launch` during composition is incorrect. Doing so will cause
launch to be called multiple times resulting in a RuntimeException.
Instead, use `SideEffect` and `launch` inside of the suspending block.
The block will only run after a successful composition.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/com/example/test.kt:10:Error: Calls to launch should happen inside
of a SideEffect and not during composition [LaunchDuringComposition]
    launcher.launch("test")
             ------
src/com/example/test.kt:15:Error: Calls to launch should happen inside
of a SideEffect and not during composition [LaunchDuringComposition]
    launcher.launch("test")
             ------
src/com/example/test.kt:20:Error: Calls to launch should happen inside
of a SideEffect and not during composition [LaunchDuringComposition]
    launcher.launch("test")
             ------
src/com/example/test.kt:30:Error: Calls to launch should happen inside
of a SideEffect and not during composition [LaunchDuringComposition]
    launcher.launch("test")
             ------
src/com/example/test.kt:34:Error: Calls to launch should happen inside
of a SideEffect and not during composition [LaunchDuringComposition]
    launcher.launch("test")
             ------
src/com/example/test.kt:41:Error: Calls to launch should happen inside
of a SideEffect and not during composition [LaunchDuringComposition]
    launcher.launch("test")
             ------
src/com/example/test.kt:46:Error: Calls to launch should happen inside
of a SideEffect and not during composition [LaunchDuringComposition]
    launcher.launch("test")
             ------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/com/example/test.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
package com.example

import androidx.compose.runtime.Composable
import androidx.activity.compose.ManagedActivityResultLauncher

@Composable
fun Test() {
    val launcher = ManagedActivityResultLauncher<String>()
    launcher.launch("test")
}

val lambda = @Composable {
    val launcher = ManagedActivityResultLauncher<String>()
    launcher.launch("test")
}

val lambda2: @Composable () -> Unit = {
    val launcher = ManagedActivityResultLauncher<String>()
    launcher.launch("test")
}

@Composable
fun LambdaParameter(content: @Composable () -> Unit) {}

@Composable
fun Test2() {
    LambdaParameter(content = {
        val launcher = ManagedActivityResultLauncher<String>()
        launcher.launch("test")
    })
    LambdaParameter {
        val launcher = ManagedActivityResultLauncher<String>()
        launcher.launch("test")
    }
}

fun test3() {
    val localLambda1 = @Composable {
        val launcher = ManagedActivityResultLauncher<String>()
        launcher.launch("test")
    }

    val localLambda2: @Composable () -> Unit = {
        val launcher = ManagedActivityResultLauncher<String>()
        launcher.launch("test")
    }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/activity/activity-compose-lint/src/test/java/androidx/activity/compose/lint/ActivityResultLaunchDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `ActivityResultLaunchDetector.errors`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=612128.

(##) Including

!!!
   This is not a built-in check. To include it, add the below dependency
   to your project.

```
// build.gradle.kts
implementation("androidx.activity:activity-compose:1.10.0-rc01")

// build.gradle
implementation 'androidx.activity:activity-compose:1.10.0-rc01'

// build.gradle.kts with version catalogs:
implementation(libs.activity.compose)

# libs.versions.toml
[versions]
activity-compose = "1.10.0-rc01"
[libraries]
# For clarity and text wrapping purposes the following declaration is
# shown split up across lines, but in TOML it needs to be on a single
# line (see https://github.com/toml-lang/toml/issues/516) so adjust
# when pasting into libs.versions.toml:
activity-compose = {
    module = "androidx.activity:activity-compose",
    version.ref = "activity-compose"
}
```

1.10.0-rc01 is the version this documentation was generated from;
there may be newer versions available.

[Additional details about androidx.activity:activity-compose](androidx_activity_activity-compose.md.html).
(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("LaunchDuringComposition")
  fun method() {
     launch(...)
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("LaunchDuringComposition")
  void method() {
     launch(...);
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection LaunchDuringComposition
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="LaunchDuringComposition" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'LaunchDuringComposition'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore LaunchDuringComposition ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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